Gymnetina Casey 1915: 284 (as a subgenus of Gymnetis). Type species: Gymnetina cretacea (LeConte, 1863) by monotypy. Elevated to generic level by Martínez (1949).

Description. Scarabaeidae, Cetoniinae, Gymnetini. Form: Rhomboidal, robust, sides slightly tapering from humeri towards apex of elytra, dorsum nearly flat. Color black to dark reddish brown, shiny, with cretaceous spots or bands on, variably, pronotum, elytra, pygidium, mesepimeron, metepisternum, metacoxa, and abdominal sternites. Surface of pygidium with short setae. Head: Shape subrectangular, longer than wide. Clypeus broadly truncate, apical angles broadly rounded, sides constricted just before antennal insertion, frons weakly, longitudinally tumid at middle. Antenna 10-segmented. Pronotum: Shape subtrapezoidal, widest near base, gradually convergent to anterior angles, basomedian lobe strongly produced, lobe covering all but tip of scutellum. Sides margined, anterior and basal margins lacking bead. Elytra: Widest at base, posthumeral emargination distinct. Bead present on lateral margin. Pygidium: Surface concentrically rugulopunctate, nearly flat to weakly convex. Venter: Mesometasternal process short, ventral surface flat with respect to ventral axis of body, apex broadly rounded. Males with abdomen distinctly concave in lateral view. Females with abdomen flat to slightly tumescent; last sternite densely punctate to transversely rugulopunctate. Legs: Protibia usually tridentate in both sexes (teeth reduced to obsolete in males of G. cretacea), teeth variably spaced. Femora and meso- and metatibiae with dense fringe of black setae. Metatibia at apex with 3 rounded to subacute teeth and with 2 long, acute spurs in males, shorter spur with slightly rounded apex in females. Parameres: In caudal view, form of both together subrectangular, apices rounded, with small tooth apicolaterally.

Diagnosis. Species of Gymnetina are distinguished by a shiny, black surface with cretaceous spots or bands on, variably, the pronotal lateral margin, elytra, pygidium, mesepimeron, metepisternum, metacoxa, and abdominal sternites; subtruncate to truncate to rounded clypeal apex; frons weakly and longitudinally tumid at middle (lacking armature); tridentate protibia (teeth occasionally reduced); and a broad, flat, apically rounded mesometasternal process parallel to the ventral axis of the body. With the exception of some species of Amithao Thomson and Halffterinetis Morón and Nogueira, no other species of New World Gymnetini have cretaceous spots or bands on a black, shiny body surface. All other American Gymnetini have a velutinous body surface or are shiny with a different color and lacking white, chalky marks. Gymnetina species are easily distinguished from Amithao Thomson species because the apex of the clypeus is broadly subtruncate to truncate to rounded in Gymnetina species, while in Amithao species it is deeply emarginate. Males of Halffterinetis gonzaloi Morón and Nogueira are similarly colored to Gymnetina species, with a black, shiny integument and cretaceous markings along the lateral pronotal margins and a cretaceous spot on each side of the pygidium. However, Halffterinetis species are smaller, lack a distinct mesometasternal process, and males lack apicolateral teeth on the parameres.